Conventionally, so-called electrically-conductive glass is well known as a transparent electrically-conductive thin layer, which includes a glass and an indium oxide thin layer formed thereon. Since the electrically-conductive glass has a glass substrate, however, it has low flexibility or workability and cannot be used for certain purposes. In recent years, therefore, transparent electrically-conductive films using various types of plastic films such as polyethylene terephthalate films as their substrates have been used, because of their advantages such as good impact resistance and light weight as well as flexibility and workability.
The conventional transparent electrically-conductive films using such film substrates not only have the problem of low transparency due to high light reflectance of the thin film surface but also have low scratch resistance or low bending resistance so that they can have problems in which they can get scratched to have an increased electrical resistance or suffer from disconnection during use. They also have the problem of low environmental resistance.
Touch panels using such transparent electrically-conductive films also have a problem in which Newton's rings can be caused by film waving or curling to degrade their visibility. To resolve this problem, for example, there is proposed a transparent electrically-conductive film including a laminate of a hard-coated film and an electrically-conductive film, wherein the difference between the longitudinal and transverse thermal shrinkage rates of a transparent substrate and a hard coat layer that form the hard-coated film is controlled to a low level (see Patent Literature 1: JP-A No. 2002-73282). The transparent electrically-conductive film described in Patent Literature 1 can hardly cause curling during heating processes, but its resistance to moisture and heat is not sufficient, and it can cause curling due to environmental change during storage, transportation or the like or can cause curling in a high-temperature, high-humidity environment. It is also proposed that a metal oxide layer and a cured layer of a shrinkable curable resin are formed in this order on the side opposite to the transparent electrically-conductive layer in the transparent electrically-conductive film so that convex curling caused by the metal oxide layer can be canceled by the cured layer of the shrinkable curable resin (see Patent Literature 2: JP-A No. 11-216794). In Patent Literature 2, a polysiloxane thermosetting resin is generally used for the cured layer of the shrinkable curable resin, but the cured layer formed by applying the polysiloxane thermosetting resin and curing it has low resistance to moisture and heat and can cause curling in a high-temperature, high-humidity environment. To resolve this problem, there is also proposed a transparent electrically-conductive film including a film substrate, hard coat layers formed on both sides of the substrate, a transparent electrically-conductive thin layer formed on one side, and a metal oxide (such as SiOx) thin layer formed on the other side (see Patent Literature 3: JP-A No. 02-5308). However, the hard coat layers formed on both sides can reduce the flexibility of the film so that the durability against pen-based input can be insufficient or cracking can easily occur during a punching process.